Peripheral Embolization Using Hydrogel-Coated Coils Versus Fibered Coils: Short-Term Results in an Animal Model

In Vitro Head-to-Head Comparison of Flow Reduction between Fibered and Non-Fibered Pushable Coils

PURPOSE

To compare the embolization effects of a non-fibered pushable coil with a conventional fibered pushable coil in an in vitro bench-top experiment.

MATERIALS AND METHODS

A simplified vascular phantom with 4 channels (1 for the non-fibered coil, 1 for the fibered coil, and 2 for continuous circuit flow) was used. A single coil of the longest length was inserted to evaluate the effect of single-coil embolization, and 3 consecutive coils were inserted to assess the effect of multiple-coil embolization. Post-embolization angiography was performed to obtain flow variables (time to peak [TTP], relative peak intensity [rPI], and angiographic flow reduction score [AFRS]) from time density curves. The packing densities of the two coil types were calculated, and the AFRS of each channel was determined by dividing the TTP by the rPI.

RESULTS

When inserting a single coil, the conventional fibered coil demonstrated better flow reduction, as indicated by a higher AFRS (25.6 vs. 17.4, P=0.034). However, the non-fibered coil exhibited a significantly higher packing density (12.9 vs. 2.4, P=0.001). Similar trends were observed with multiple coils.

CONCLUSION

The conventional fibered pushable coil showed better flow reduction efficiency, while the non-fibered pushable coil had a higher packing density, likely due to the flexibility of the coil loops. A better understanding of the distinct characteristics of different pushable coils can enhance the outcomes of various vascular embolization.

Coils embolization use for coronary procedures: Basics, indications, and techniques

The use of coils is fundamental in interventional cardiology and can be lifesaving in selected settings. Coils are classified by their materials into bare metal, fiber coated, and hydrogel coated, or by the deliverability method into, pushable or detachable coils. Coils are delivered through microcatheters and the choice of coil size is important to ensure compatibility with the inner diameter of the delivery catheter, firstly to be able to deliver and secondly to prevent the coil from being stuck and damaged. Clinically, coils are used in either acute or in elective setting. The most important acute indication is typically the sealing coronary perforation. In the elective settings, coils can be used for the treatment of certain congenital cardiac abnormalities, aneurysms, fistulas or in the treatment of arterial side branch steal syndrome after CABG. Coils must always be delivered under fluoroscopy guidance. There are some associated complications with coils that can be acute or chronic, that nictitates regular followed-up. There is a need for education, training and regular workshops with hands-on to build the experience to use coils in situations that are infrequently encountered.

Vascular occlusion with 0.035-inch hydrogel expandable coils in congenital heart diseases and vascular anomalies

BACKGROUND

We present our experience with transcatheter vascular occlusion using 0.035-inch hydrogel expandable coils, which has been reported only in a few cases in the pediatric cardiology fields.

METHODS

This study is a retrospective analysis of all patients who underwent transcatheter embolization with 0.035-inch hydrogel coils at the Department of Pediatrics, Okayama University Hospital, between October 2018 and September 2020.

RESULTS

Twenty patients with a median age of 5.1 years (0.05-26.0 years) and a median weight of 13.8 kg (3.0-56.8 kg) were included. A total of fifty-four 0.035-inch hydrogel coils, including 35 Azur 35 and nineteen Azur CX 35 coils (Terumo, Tokyo, Japan), were successfully deployed in 22 target vessels. The target vessels consisted of 10 aortopulmonary collaterals, 8 veno-venous collaterals, and 4 pulmonary arteriovenous malformations. We achieved technical success in all the target vessels. In total, the mean target vessel diameter was 4.4 mm, the mean number of 0.035-inch hydrogel coils was 2.5 per vessel. The mean device to vessel ratio was 1.6 for the anchor coil and 1.2 for the additional coil. Post-implantation angiograms revealed that the primary occlusion rate was 18/22 (82%). There were no periprocedural complications.

CONCLUSIONS

The 0.035-inch hydrogel expandable coils are effective and safe in patients with congenital heart disease and vascular anomalies. These occlusion devices could be valuable options for interventional pediatric cardiologists.

Vessel Occlusion using Hydrogel-Coated versus Nonhydrogel Embolization Coils in Peripheral Arterial Applications: A Prospective, Multicenter, Randomized Trial

PURPOSE

To evaluate the safety and effectiveness of hydrogel-coated coils for vessel occlusion in the body trunk.

MATERIALS AND METHODS

A total of 77 patients with various peripheral vascular lesions, treatable by embolization with coils, were randomized (hydrogel group, n = 38; nonhydrogel group, n = 39). In the hydrogel group, embolization of the target vessel was conducted using 0.018-inch hydrogel-coated coils (AZUR 18; Terumo Medical Corporation, Tokyo, Japan) with or without bare platinum coils. The nonhydrogel group received both bare platinum coils and fibered coils without the use of hydrogel-coated coils.

RESULTS

Complete target vessel occlusion was accomplished in 36 patients in the hydrogel group and 37 patients in the nonhydrogel group. No major adverse events were observed in either group. The median number of coils/vessel diameter and the median total coil length/vessel diameter were significantly larger in the nonhydrogel group than in the hydrogel group (P = .005 and P = .004, respectively). The median embolization length was significantly longer in the nonhydrogel group (31.95 mm) than in the hydrogel group (23.43 mm) (P = .002). If no expansion was assumed, the median packing density in the hydrogel group was 44.9%, which was similar to that in the nonhydrogel group (46.5%) (P = .79). With full expansion assumed, the median packing density in the hydrogel group was 125.7%.

CONCLUSIONS

Hydrogel-coated coils can be safely used for peripheral vascular coil embolization, and hydrogel-coated and conventional coils in combination allow for a shorter embolization segment and shorter coil length.

Temperature-induced configuration changes in hydrogel-coated coils and their relevance in embolization procedures

Background

The present study attempted to demonstrate how the configuration of hydrogel-coated coils is influenced by different temperature exposures.

Thirty detachable hydrogel-coated coils were evaluated in an in vitro water immersion test under five different temperature ranges (22.6 °C, 37 °C, 40–50 °C, 50–60 °C, and 60–70 °C). The configuration changes were classified (configuration I, configuration II, and configuration III) according to the curling that occurred during 30 min of immersion. Configuration stability of five Hydrogel-coated coils was also evaluated in a two-step temperature immersion test.

Results

All hydrogel-coated coils showed some configuration changes during water immersion. However, a logarithmic transformation of the time and temperature data showed a significant (p < 0.05) negative linear correlation between time and temperature for all coil configurations (configuration I: R = 0.97, configuration II: R = 0.98, configuration III: R = 0.97). The time needed to reach configuration III (complete coiling) was 160.4 ± 41.9 s at 37.5 °C (range: 100–205 s), 45.7 ± 22.2 s at 47.5 °C (range: 23–70 s), 20.2 ± 7.2 s at 57.5 °C (range: 14–32 s), and 10.3 ± 2.4 s at 67.5 °C (range: 7–13 s).

Conclusions

Temperatures above 55 °C induced immediate configurational changes in the hydro-coated coils, achieving complete curling within less than 30 s. Temperatures near 36 °C (normal body temperature) require more time to reach optimal coil curling (configuration III). The optimization of HydroCoil preparation can reduce interventional procedural time and improve clinical results.

A Preclinical Porcine Model of Portal Vein Thrombosis in Liver Cirrhosis

Background

This study aimed at presenting a novel method of developing a porcine model of portal vein thrombosis (PVT) in cirrhosis by intravenous administration of thrombin and insertion of a fibered coil. We further investigated changes of biochemical parameters, coagulation, and proinflammatory cytokine expression in the cirrhosis-PVT group.

Methods

Twelve male pigs were randomized into the control group (n = 3) and cirrhosis group (n = 9). In cirrhotic pigs, three were randomly selected to establish PVT by ultrasound-guided percutaneous puncture of the main portal vein (MPV) followed by intravenous thrombin administration and fibered coil insertion. Thrombosis in the MPV was detected by abdominal enhanced computer tomography (CT). The changes of hepatic function, coagulation system, and inflammation cytokines were compared among normal, cirrhosis, and cirrhosis with PVT groups.

Results

As manifested by the presence of a filling defect in MPV on portal venous-phase CT angiography, fibrin thrombi were formed in the MPV in cirrhotic pigs within one week and persisted for four weeks. Five weeks after surgery, abnormal liver functions occurred in association with PVT formation in cirrhosis. Both coagulation and thromboelastography parameters showed that cirrhosis-PVT pigs exhibited a procoagulant state through hyperfunction of platelets and clotting factors. Interleukin 6 (IL-6) as a potential inflammatory marker stimulated PVT-mediated inflammation activation in cirrhosis.

Conclusions

Our study provides in vivo evidence that intravenous injection of a coil and thrombin into MPV under interventional guided devices enables a feasible method in thrombus creation. Further exploration and validation of large-sample cases are required to characterize utilities of this model.

Midterm Recanalization after Arterial Embolization Using Hydrogel-Coated Coils versus Fibered Coils in an Animal Model

PURPOSE

To compare angiographic and pathologic effects (ie, occlusion, recanalization) after embolization with Hydrogel-coated coils (HydroCoils) and fibered coils in the renal and internal iliac arteries after 7 days and 1 and 4 months in an animal model.

MATERIALS AND METHODS

Twelve sheep had 1 internal iliac and 1 renal artery randomly embolized with HydroCoils or fibered coils. Renal and internal iliac arteries were embolized with detachable 0.018-inch coils and pushable 0.035-inch coils, respectively. All animals had control angiography performed at 7 days, and 1 and 4 months to assess recanalization before euthanasia. Recanalization and inflammation were evaluated via pathologic examination.

RESULTS

At 1 month, 100% of arteries embolized with HydroCoils were occluded vs 50% of those embolized with fibered coils (P = .004). At 4 months, 80% of arteries embolized with HydroCoils were occluded vs 25% of those embolized with fibered coils (P = .01). Surface of vessel occlusion was significantly greater for iliac arteries (96.7% ± 8.9) than for renal arteries (94.2% ± 5.3; P = .0076). Surface of occlusion of the renal arteries (92.2% ± 5.1) was lower for fibered coils than for HydroCoils (96.8% ± 4.7; P = .0287). Surface percentage of thrombus was significantly lower for HydroCoils than for fibered coils (P < .0001). Surface percentage of thrombus was correlated with surface percentage of recanalization (P = .0181).

CONCLUSIONS

After 4 months, 75% of arteries embolized with fibered coils were recanalized vs 20% of those embolized with HydroCoils (P = .01). Reduced amount of thrombus after embolization with HydroCoils accounted for a reduced rate of arterial recanalization.

Histopathological differences of experimental aneurysms treated with bare platinum, fibered, and bioactive coils

PURPOSE

To evaluate the histopathological features of experimental aneurysms embolized with bare platinum, fibered, and bioactive coils.

MATERIAL AND METHODS

Twelve experimental aneurysms were constructed in three swine. The aneurysms were divided into four groups and were embolized using a bare platinum coil alone (P group, n = 2), a bioactive coil alone (B group, n = 2), a combination of fibered and bare platinum coils (F/P group, n = 4) and a combination of fibered and bioactive coils (F/B group, n = 4). Histopathological data for all aneurysms recorded at 63 days were analyzed in terms of neointima formation, fibrosis, foreign-body giant-cell infiltration, and organization.

RESULTS

Fibrosis was significantly greater in group B compared with that in group F/P (p = .02).　 Inflammation with foreign-body giant-cell infiltration was significantly greater in groups F/P and F/B compared with that in groups P and B (p = .007).

CONCLUSION

The present study revealed that the embolic effect of fibered coils was not a thrombus but instead was a foreign-body response in the chronic phase.